Recent Completed Project on Metallography, Accelerated Rupture Testing and Remaining Life Assessment of Superheater & Reheater Tubes

1630.jpg

ETD is pleased to announce the successful recent completion of a metallography, accelerated rupture testing and remaining life assessment project of superheater & reheater tubes.

It is reported by the client that they had hired a sub-contractor to perform accelerated rupture testing and remnant life assessment work for 1 superheater and 1 reheater tubes (of T91 materials). This contractor had completed the creep test and RLA based on an iso-thermal basis with reference to Manson-Haferd curve. Recently, the client hired a second contractor to do the same job. This second contractor had done the creep test and RLA based on an iso-stress basis. The actual service stress in this case is relatively low. The client had found that the results from these two contractors differed greatly; the results of second contractor showed unrealistically high remaining life and they did not consider progressive wastage.

Therefore, ETD was approached with a request to perform the same work (accelerated rupture testing and RLA) again for these two coal-fired tubes to provide an estimate for the remaining life of the components.

The scope of the work carried out included the following tasks:

i.  Metallography - Metallography of two tube samples were carried out to establish the creep damage (i.e. creep cavitation & microstructure degradation) levels. The microstructure and any degradation characterised using damage classification for creep damage of the relevant materials. Specific scope in this task included:

  • Visual examination of the tube samples including internal and external appearance;

  • Assessment of condition of internal and external surfaces including identification of inclusions/ contaminations, scale/ deposits, welding defects etc (if any exists) and obtain photos of evidence;

  • Dimensional examination - OD measurement at 12-6 and 3-9 O’clock positions at fixed length intervals throughout the entire tube length.

  • Tube wall thickness measurements for all aforementioned clock positions.

  • Metallographic examination of the tube samples using optical microscopy to assess the condition of internal and external surfaces, to identify phase changes in microstructure / material degradation/ precipitations and also to identify the damage mechanism(s);

  • Estimation of tube operating temperature based on measurements of steam-side oxide thickness;

  • Hardness testing and evaluation to determine the equivalent tensile strength values (using published hardness/ UTS correlation tables) to assess the mechanical strength or softening of the materials.

ii.  Accelerated Stress Rupture Testing - A programme of isothermal rupture testing was then performed comprising three specimens from each of the two tube samples to be tested. The tests were performed at conditions designed to achieve target durations of 500, 1000 and 3000 hours as proposed by ETD. After reviewing the design and operating parameters, the test conditions (i.e. temperature, stress etc) was selected by ETD based on previous experience and reference database to give failures at the above number of hours.

All these tests will be conducted by ETD’s collaborative accredited laboratory in Europe and according to the international and ECCC specifications.

iii.  Analysis of Creep Test Results and Remaining Life Calculations - The results from the above rupture testing programme were compared with standard data for the relevant steel grade to establish where, within the upper and lower bounds, the material creep properties lie. Hence an equation describing the actual creep strength of the ex-service material being modelled. This equation was then used to estimate the creep life at the service conditions.

Provided that the as-installed tube wall thickness and service hours to date are known, then the corrosion rate (wall thinning rate) can be calculated using the thickness measurements from the first task. This corrosion rate was used to determine the combined effect of creep and corrosion on the component remaining life at the effective operating temperature estimated in the first task.

A final report, detailing the findings of the tasks undertaken, was issued for comments by the client. It will include photographic records from the metallographic study and provide details of the remaining life estimate based on accelerated rupture testing. Any possible causes for concern will be highlighted. The influence of material degradation and other microstructural changes were also discussed in this report.

For more information about our life assessment services please click here.

Recent Completed Project on Inspection, Fitness for Service and Life Assessment of T-piece Welded Piping

1634.jpeg

ETD is pleased to announce the successful recent completion of an inspection, fitness for service and life assessment project for a European based plant.

In October 2017, microcracks were observed on a welded T-piece of main steam balancing pipe connections. Defect/ crack assessment was performed by the plant engineers and the results showed that the component will be fit for service for another 4 years with the repair of cracks by burring techniques. However, these results were not acceptable by the owners and insisted further analysis would be performed. The results of the second assessment showed that the component should be replaced as early as possible. Due to the disagreement between the owners and plant management, a decision was made that further analysis would be performed by an independent third party and then make appropriate decision for run/repair/replacement of the component. Therefore, ETD were asked to submit a proposal to perform further inspection and analysis to assess fitness for service and predict remaining life and of the component.

ETD proposed to carry out the project in the following two phases. The objectives and scope of work for each phase are:

Phase 1:

(i) Review two previous reports - defect assessment and life assessment reports completed by the client.

(ii) Perform onsite inspection. This will include the followings:

  • On-site replication at 4 clock positions for the affected T-piece of the balancing pipe connection;

  • On-site hardness testing at the same locations as the replication spots;

(iii) Review design and operating parameters, previous failure and maintenance history;

(iv) Perform condition assessment and fitness for service assessment based on the damage classification.

(v) Report covering the results of the investigations & provide recommendations on whether the component is fit for service.

Phase 2:

(i) Perform pipeline stress analysis of the piping system to obtain line loads and bending stresses which will be used in Finite Element (FE) analysis. This will include the following Tasks:

  • Review of design/ isometric drawings clearly showing all dimensions and piping connections of the piping system.

  • Review and analysis of inspection data/ information of hangers and supports collected during hot and cold condition inspection.

  • Perform pipeline stress analysis of the piping system using CAESAR II software.

(ii) Perform Finite Element (FE) analysis to obtain accurate stress levels at the affected T-piece location of the balancing pipe.

(iii) Perform remaining life assessment using the stress values obtained from FE analysis.

A report was then issued detailing the findings with photographic records including results of stress analysis & life assessment and highlighting any possible causes for concern regarding the pipe integrity. Furthermore, the report included recommendations for possible remedial actions that may improve component integrity.

For more information on our life assessment services, please click here.

Offer of Unique P91, P92 Services for New & Running Plants

In this P91/P92 Services Brochure you will find useful and interesting information on ETD’s unique P91, P92 Services for New & Running Plants. These include:

a) Inspection, Monitoring, Assessment & Life Extension Services: Over the last decade through its collaborative research programmes, with its international industry partners, involving large pipe testing ETD has developed a suite of specialist inspection and monitoring techniques and life assessment methodologies that it offers to plants worldwide. These are offered in addition to the conventional NDE techniques for the detection and sizing of defects, together with replication and portable hardness testing for component condition and remaining life assessment. ETD carries out code-based calculations of creep life using either deterministic or probabilistic (another of ETD specialities) methodologies. Examples of these techniques include: Scanning Force Microscope (SFM) for early stage damage detection, Miniature sample removal (boat sampling) for quality checks and life/condition assessment, Precision Portable Hardness Tester (known as ‘Smart sleeve’), ‘Obikou’ for Pipe Strengthening and Life Extension and Defect/Crack Assessment.

 b) Root Cause Failure Analysis: Over the years ETD has developed an expertise in the root cause failure investigation of P91 and P92 components/welds. In the recent past, ETD has investigated a range of failures of T91 tube components and welds, and cracking in P91 pipes and drain-line components in conventional boilers and HRSGs. In these investigations, ETD identifies the root cause of the damage, and proposes remedial actions and solutions to the problem.

c) Consultancy & Guidelines on Materials & Welding: ETD provides P91 and P92 users with advice and guidance on the metallurgy, welding and heat treatment of these steels. This service includes reviewing weld procedure specifications (WPS) for similar and dissimilar metal welds, inspection of NDE records, and guidelines for repair welding of P91. The advice is provided to both the plant operators and designers/ manufacturers. This advice is based on ETD’s P91 experience in a number of Group Sponsored Projects including its running of the International P91 Users Group (Int. P91UG) for international industry over more than a decade and its involvement as consultants to many a power plants worldwide.

For further details of our P91/P92 services and opportunities being offered, please click on the image above.

Offer of Both Traditional and Innovative Plant ‘Inspection’ & ‘Life Assessment’ Services

In this Plant Services Brochure you will find useful and interesting information on ETD’s plant inspection and integrity/ life assessment services. These include:

a) Traditional NDE inspection: Using, for example, Boroscopy, PAUT (Phased Array Ultrasonic Testing), EMAT (Electromagnetic Acoustic Testing), PEC (Pulsed Eddy Current), LFET (Low Frequency Electromagnetic Testing), Replication (including replica assessment), Hardness testing, Wall Thickness profiling, Oxide Thickness measurement etc.

b) New state-of-the-art Innovative NDE Inspection Techniques: Developed through ETD’s collaborative joint industry projects. This includes equipment such as (details later in this brochure): a) Portable spark erosion ‘boat sampling’ machine (called EDSE), b) Portable Scanning Force Microscope (SFM) for on-site early stage nano and micro level damage detection especially in materials like P91, c) ‘Obikou’ pipe reinforcement technique which offers creep life extension of creep damaged seamless or seam welded pipes, by simply and quickly reinforcing them with multiple layers of a thin high-temperature alloy strip, and, d) Our newly invented first of its kind portable ‘precision’ hardness tester, called ‘Smart Sleeve’, which improves the accuracy of the ‘MIC 10’ or other portable hardness testers.

c) Integrity/ Life Assessment: In addition to inspection, ETD offers independent and impartial plant safe remaining life assessment using both deterministic and probabilistic techniques. It has its own software for crack assessment, RBM/ RBI and carries out routinely both root cause failure analysis (RCA), replica and life extension/ assessment for pressure parts and turbine components and RCM.

Details of the services and opportunities being offered can be seen by clicking on the image.

ETD's ‘HIDA-7’ Conference – Special Issue now published in the ‘Materials at High Temperature’, journal

ETD Consulting are pleased to announce that following its successful High Temperature Defect Assessment (HIDA-7) Conference on the subject of Life/Crack Assessment and Failures in Industrial Structures, in particular those operating at high temperature, which was held at Portsmouth University in May 2017; edited versions of several of the papers presented at this conference have now been published in the ‘Special Issue of Materials at High Temperature’ journal.

HIDA was originally the acronym for an EU Commission and Industry supported research project, led by Dr Ahmed Shibli of ETD, which aimed to develop a unified European High Temperature Defect Assessment procedure. The Brite-Euram HIDA project involved 11 organisations from 7 countries, with the effectiveness of the procedure developed being demonstrated using material models based on data generated and/or gathered on a number of CrMo(V), 9CrMoVNb and 17Cr12NiMo engineering steels. The original HIDA conference held at CEA (Saclay) in 1998 focused on the themes covered by the Brite-Euram project, and in particular topics concerned with crack growth and accurate assessment of the behaviour of high temperature plant components containing defects and operating under steady and/or cyclic loading conditions. The scope of subsequent HIDA conferences was extended to the consideration of aspects relating to life assessment and condition monitoring, integrity of repaired welds and the characteristics and performance-in-service of newer advanced martensitic steels such as P91 and P92.

The 22 papers included in MHT’s HIDA-7 Special Issue fall under the themes:

  • Deformation and crack growth and their modelling;
  • Life assessment and condition monitoring;
  • Advanced martensitic 9/10%Cr steels;

To read the full-depth article from the special issue of materials at high temperatures magazine, please click here.